1. Field of the Invention
The present invention relates to a mist trap mechanism and method for a plating apparatus for removing a mist from an atmosphere which is discharged from a plating space, and particularly a mist trap mechanism and method for a plating apparatus, which are suitable for improvement of a mist removing effect.
2. Description of the Related Art
In production of a semiconductor device or a flat-panel display device, there is used a process for forming a film of copper (Cu), which is a wiring material, by plating in order to form fine wiring on a subject substrate such as a semiconductor wafer, a glass substrate or the like.
Such a plating process is performed by filling a plating solution, e.g., an aqueous solution containing CuSO4 as a base, into a plating solution bath and immersing the subject substrate, which is previously formed a thin film layer (seed layer) as a seed for plating, into the plating solution.
In addition to CUSO4, the plating solution generally includes H2SO4 which increases conductivity to finely pass a plating current so to make efficient plating and an additive for plating uniformly so to maintain the quality. Therefore, the plating solution is generally high in corrosion because of H2SO4 included.
Therefore, a general apparatus for plating is provided with a processing space which surrounds the plating solution bath to shut off from the outside atmosphere. Thus, a mist of corrosive plating solution or scattered plating solution resulting from the plating solution filled in the plating solution bath is kept in the processing space and prevented from diffusing to the outside.
However, even if the mist of plating solution is simply held in the processing space, the atmosphere in the processing space is degraded and a trouble is caused in the processing or the apparatus. Specifically, the mist of plating solution becomes a contamination source to the subject substrate when the subject substrate is through the plating process and pulled upward and held above the plating solution bath.
The mist of plating solution has an effect on a dry contact for performing electrical contact with the subject substrate, which is disposed on a subject substrate holder which holds the subject substrate, immerses it in the plating solution bath and takes off it from the plating solution bath. Specifically, a surface of the dry contact is corroded with the mist of plating solution in the processing space and the corroded surface becomes a cause of increasing a contact resistance. Besides, the mist of plating solution adheres to the inside surface or the like which forms the processing space to produce deposition or the like of CuSO4 and to increase a load of maintenance.
To remedy such defects and to keep the atmosphere in the processing space clean, a gas discharge portion for discharging the atmosphere from the processing space is generally disposed. From the viewpoint of the prevention of the corrosive substance from diffusing to the outside, this gas discharge portion is desired to remove the mist of plating solution, which is contained in the discharge gas, in an amount as large as possible.
However, to effectively remove the mist of plating solution which is contained in the atmosphere discharged from the processing space, it is generally necessary to adopt a method which uses a large amount of liquid for dissolving the mist and separating it from a gas such as air and passes the discharge gas through the liquid so that its contact area with the liquid becomes large. This method requires a large-scale apparatus, which is not suitably fitted to the plating apparatus.
The present invention was achieved in view of the above circumstances. It is an object of the invention to provide a mist trap mechanism and method for a plating apparatus, which remove a mist from the atmosphere to be discharged from a plating space, wherein a mist removing effect can be improved by a simple structure.
To achieve the above object, a mist trap mechanism for the plating apparatus according to the present invention comprises a gas discharge passage which runs from a space in a plating chamber to a space outside the plating chamber; a liquid spouting portion which is disposed in the gas discharge passage and spouts a liquid to be collided with a stream of gas being discharged; a solid wall which is disposed in the gas discharge passage in such a way that its surface gets wet with the spouted liquid and the wet surface collides with the stream of discharge gas; and a liquid recovery portion which is disposed in connection with the gas discharge passage and recovers the spouted liquid, the liquid collided with the stream of gas and the liquid having wetted the surface of the solid wall.
The gas discharge passage is disposed to connect the space in the plating chamber and the space outside the plating chamber. The gas discharge passage is provided with the liquid spouting portion and the solid wall, the discharge gas collides with the liquid spouted from the liquid spouting portion, and the discharge gas collides with the solid wall whose surface is wetted with the liquid spouted from the liquid spouting portion. Such a two-stage collision applied to the discharge gas allows effectively taking the mist contained in the discharge gas into the liquid. It is because the discharge gas is passed through the gas discharge passage which is a passage having a limited size, and the aforesaid collision gives a large impact to the discharge gas. Besides, the liquid recovery portion which is disposed in connection with the gas discharge passage allows collectively catching the mist in a state taken into the liquid.
Therefore, the mist removing effect in the processing space can be improved by a simple structure, and when the mist trap mechanism is fitted to the plating apparatus, its mounting position can be selected with high flexibility.
The mist trap method for a plating apparatus according to the present invention comprises discharging a gas from a space in a plating chamber to a space outside the plating chamber through a gas discharge passage; colliding liquid spouted from a liquid spouting portion, which is disposed in the gas discharge passage, with a stream of the discharge gas; colliding the stream of the discharge gas with a solid wall which is disposed in the gas discharge passage and has its surface wetted with the spouted liquid; and recovering the spouted liquid, the liquid collided with the stream of gas and the liquid having wetted the surface of the solid wall.
This method has substantially the same function as that of the mist trap mechanism for the plating apparatus and can have substantially the same effect.